Process of purifying caustic aluminate liquors



April 25, 1961 PROCESS OF' PURIFYING-CAUSTIGALUMIN 4 Sheets-Sheet lFiled Deo. 1, 1952 i HVSA vant. OF

April 25, 1961 J. L.. PORTER 2,981,600

PROCESS 0F PURIFYING CAUSTIC ALUMINATE LIQUoRs Filed Dec. l, 1952 4Sheets-Sheet 2 April 25, 1961 J. l.. PORTER 2,981,600

PROCESS OF PURIFYING CAUSTC ALUMINATE LIQUORS Filed Deo. 1. 19452 4Sheets-Sheet 3 BLUMlN-VCAUSTXC SODA RATIO VS. TIM? LGEND o Pumxzn ,mavenn nLisNDED manon A PLBNT LIQUOR -cnus'rc s oDA Rfvrlo u o s 1o 1s 2o 25so sa 4o 45 Pncxm'r'rxon TIME. HOURS INVENTOR. JQHN 1.,. PORTER ATTORNEY`organic substances, such as sodium `nated withL theseorg'anicsubstances:` ori sodi kcompounds designated collectively-,assodiumyorganates) ,i ,t and also( sodium tfcarlzronate,` the latterrepresenting 1 Athe UnitedStates Patent PROCESS OF PURIFYING CAUSTICALUMINATE LIQUORS Filed Dec. 1, 1952, Ser. No. 323,414

2 Claims. (Cl. zii- 143) The present invention relates to a process forthe treatment of caustic aluminate liquors such as are used in theproduction of alumina from aluminous ores by the wellknown Bayerprocess. More particularly, the invention relates to a process for thepurification of contaminated Bayer process liquors to establish and/ormaintain improved conditions for clariiicationof the liquor containingthe residue of the digested ore and for the precipitation of the aluminafrom the claried liquor. Specifically, the invention is directed to aprocess which accomplishes the removal and degradation of organicsubstances in the liquors, which act as settling inhibitors duringclarification and `which also adversely affect precipitation of aluminafrom the clarified liquor. The process further provides a means forcontrol of process carbonation by rectification of non-caustic soda intocaustic soda for reuse in the Bayer process. This application is acontinuation in part of my copending application,

Serial Number 262,808, iled December 2l, 195,1, and

now abandoned. .t The well-known Bayer process is universally operatedon a continuous basis and involves pressure digestion of aluminous ores,such as bauxites and laterites, in caustic aluminate-liquor of varyingcaustic soda concentration and at elevated temperatures depending uponthe type of ore to extract the available alumina. The caustic liquorenriched in sodium aluminate is then subjected to clarification bysettling, washing, and filtering to remove the so-cal1ed red mud residueof the ore which `consists primarily of hydrated ferrie oxide and adesilication product. Alumina is thenauto-precipitated `from the`clarified green liquor by decomposition` of sodium aluminate throughseeding withpreviously precipitated alumina and the spent caustic liquoris recycled to the digestion phase,

amounts of make-up caustic liquor.`

STATEMENT or` PaoBLEM usually after` reconcentration and additionfofrequired soda. The liquor also containsrelatively largequantities ofdissolved sodium carbonate andlsmaller quantities of a complex-mixtureof solubilizedorldissolved sodium organic compounds including salts,`which are formed in the v,caustic liquor 2,981,600 Patented Apr. 25,1961 so-called process carbonation of the liquor, a term used generallythroughout the industry. Process carbonation involves the accumulationof sodium carbonate in the liquor through (1) the progressivedegradation of sodium organic compounds of more or less higher molecularweight into this more or less ultimate form, (2) pick up of carbondioxide in the atmosphere by the caustic soda, and (3) introduction ofsoda ash as such into the process liquor from the lime-soda causticizingreaction when conducted outside or inside the main liquor system.

This contaminating fraction of the total sodium or soda (NazO) contentof the liquor is denominated herein as the non-caustic soda, since it isnot present as free caustic soda and is not available to form sodiumaluminate. The fraction of the non-caustic soda which includes theorganic substances or sodium organates is designated herein asnon-alkaline soda, since it comprises sodium compounds which are notacid titratable. The balance of the non-caustic soda is sodiumcarbonate. Thus, non-caustic soda=nonalkaline soda (sodium organates)+Na2CO3. i

The process carbonation in the liquor must be controlled to preventexcess accumulation of sodium carbonate which serves no useful purposeand represents an inventory of causticizable soda which must beutilized. Moreover, it is recognized that sodium carbonate interfereswith auto-precipitation of alumina from the claried liquor,` probably`through some effect on the decomposition reaction or solubility ofalumina. In addition, sodium carbonate reduces to some extent thesettling rate `of the red mud in the clarification phase of the process.

`The non-alkaline soda (sodium organates) constitutes Nevertheless, itgives rise `to a most serious problemin that at least a portion thereofexertsa powerful inhibiting action on the settling of the red mud or oreresidue during clarification of the liquor. In addition, it haspreviously been recognized that or ganic matter in the liquor inhibitsauto-precipitation of alumina from sodium alurninate liquors. Thisadverse effect on the settling rate of the red mud in the increasinglycontaminated liquor is reiiected in actual practice by an increasedstarch consumption based `on the amount or weight of red mud which canbe settled at any given rate. However, increasing starch feed rateaggravates the problem 'by increasing` the net concentration of organicmatter as sodium organates (non-alkaline soda) in q the liquor, sincethe starch degradation products, as well as sodium organic compoundsfrom the organic matter in the ore, include potent settling inhibitors.This cumulative effect is also reilectedby furtherY inhibition ofthe1auto-precipitation rate. i

A substantial :control ofprocess carbonation" in `the Bayer process isafforded by so-called inside causticizing wherein the dime-soda reactionto produce the required caustic soda `is conducted in the mainprocessliquor `stream in the` digesters. A, certain ,quantity of the limecharged is'usedto causticize al substantial portion` of the from theorganic matten-such as humus, presentin the i i ore, and fromthestarchWhichis generallyernployed as a flocculating agent in settling theredmud residue of the o (NazO) imparts the typical'darlrcolor to therecycled sodium carbonate `formed by process carbonation.` Thus,

a desired low level of sodium carbonate is maintainedin u the Irecycledliquor. ,u Inside causticizing, however, ca nnot function tosubstantially reduce the non-alkaline'soda Iconcentration, sinceitrenioves only smalliamounts of i perhaps as insolublecalciumgoomfr.eL,` sodium organate, contamination is substantially "controlled"'I'hisfactor left 'uncontrolledmaylnot se'iji- `-ously interfere with`the Bayer processes practiced on a. i f

whiglr1gradej trihydrate;` alumina ore, falthough a `definite""realizledffshould.soin contol `means befniade available' the `sodiumorganates, pounds.

Gf perhaps greater signicance is the fact that inside causticizing is ofdeiinitely limited application. This procedure can only be efficientlyutilized where the ore being extracted contains substantially all of itsYalumina as the relatively highly soluble trihydrate whereby the causticsoda concentration of the liquor may be maintained correspondingly low(eg. '180 grams per liter NaOH as equivalent Na2'CO3).

In the production of alumina from ores 'of `lower grade which contain aportion of the alumina as monohydrate, and particularly from ores of theEuropean type wherein all of the alumina is inthe form of the 'lesssoluble monohydrate, the concentration of Ycaustic soda ,in the vliquormust be substantially higher than when extracting an `all trihydratealumina ore. As a consequence, inside causticizing cannot be practicedsince the-relatively'jhigh caustic soda" concentration of the .liquorseverely Freduces the efficiency or degree of :completion .of the'lime-,soda 'equilibrium reaction. Accordingly, sorne means other thanlime causticizing must be adopted to'control process carbonation andmaintain the sodium Ycarbonate concentration at a sufficiently 'lowlevel when processing lower grade or monohydrate ores. lIn oneof itsmore important aspects, the present invention is directed to aparticular manner of effective control of process carbonation andrecovery of the sodium carbonate as caustic soda while concurrentlysubstantially freeing the liquor of settling inhibiting sodiumorganates.

Of vital importance in the necessary production of alumina from thelower grade aluminous ores is the effect of the settling inhibitorportion of the non-alkaline soda (sodium organates). Most oi the lowergrade ores, such as the West Indian bauxites and laterites, containlarge fractions of mud residue (hydrated ferrie oxide) ot a yhighlydispersible, slow or substantially non-settling nature. Moreover, theselower grade ores contain higher amounts of organic matter, such ashumates yand the like, `than the high grade trihydrate ores. Thus, thenon- ,alkaline soda concentration of the circulating process `liquorbuilds up to a higher level. This combination of factors actually leadsto the result that no practical `settling rate -for the red mud can beobtained without lutilization of excessive quantities of starch. Asindicated Vabove, excessive starch consumption increases theconcentration of 4non-alkaline soda, including settling inhibitingesodium organates, in the recycled liquor through degradation of thestarch and the net effect after repeated recycling of the liquor isnegative on the red mud settling `rate and a further inhibition of theauto-precipitation reaction. Accordingly, efficient processing of lowergrade aluminous ores by the Bayer process without control of thedeleterious sodium organates A(nonalkaline soda) is not attainable. Y vv Y The invention is according'glydirecteqd` in itsmost importantspectto olisetting these adverse effects of the Vorganic substances inthe non-alkaline soda while `concurrently providing a control of processcarbonation and recovery of Ithe `soda (Na20) as caustic soda;

oarnc'rs It is, therefore, a primary object and purpose of the1inventlon to provide a process for the treatmentv of coned, nand thenon-caustic soda of the jliquor is rectified to caustic soda.V l

-' further'object is'to provide a purification process for establishingand/ormaintaining improvedconditions for clariiication of Bayer processliquors containing the resi- "due ofthe ldigested ore'and forprecipitation of alumina Amore specific object otthe invention toprovide l @a ltreatrnentfor valkali alunijinate'liquors whereby the'Bayer/.processie rendered-lamer;

A44 Y alumina from lower grade aluminous ores containing relativelylarge amounts ofhighly dispersible residues.

A specic object of the invention is to provide a process yfor removaland separation of a substantial portion of the sodium carbonate in thecirculating caustic aluminate liquor, and for removal and separation,and degradation, of the non-alkaline soda of the liquor which inhibitssettling and autoprecipitation, and rectification of the removed andseparated non-caustic soda to caustic soda for reintroduction into themain process liquor.

A further specific object of the invention is vto provide a process forpurifying contaminated caustic aluminate liquors to improve settlingrates of the red mud residue, to reduce starch consumption -in theclarication phase, to improve the rate of precipitation ot alumina, andto reduce losses of soda in the mud washing and alumina precipitationphases of the wet alkali aluminate process.

A yfurther object and feature of the invention is to provide forselective separation of the removed sodium carbonate and the removednon-alkaline `soda ,(sodium organate.) to advantageously lpermit directcausticizing of the former with minimum loss of alumina, and to permitmoreeconornical recovery of both soda and alumina 'from the latter.

These and other objects and advantages of theinvention will becomeapparent from the `following detailed Adescription thereof.

LIQUOR `Punta,ICA-Trou The invention in its most Ygeneric aspectembraces the `treatment of caustic aluminate liquors containing sodiumorganic compounds (sodium organates) comprising concentrating the liquorto obtain a precipitated sludge of sodium organates and separating theresulting -sludge'from Vthe liquor. The sludge is a gelatinous slimyprecipitate, the identity of whichis unmistakable so that it suffices tostate that the liquor should be concentrated suiciently to obtain thistype of precipitate.

Y The separation of this sludge from the concentrated liquor is criticalto substantially complete realization of the objective Yof removal ofthe organic settling inhibitor compounds which may be contained therein,and consequent increase 4in the red mud settling 4rate and starchetectiveness. It has been found according to the in vention that inactual large scale practice centrifuging is r`the best means ofclarifying the concentrated liquor and separating the sludge in the formof a relatively high solids slurry. However, other methods of separationmay be employed, such as filtration, which is suitable in treating smallquantities of liquor but not recommended for large liquor volumes'due tothe slow iiltering'naturc of the sludge.

In referring to liquor purication bythe present invention it is to beunderstood that Ythe step of concentrating the liquor' accomplishes adecontamination beyond a reduction in settling Vinhibitor content byprecipi- VVtation and removal of a substantial portion of the non-`products areV evidentlyformed, some of which are insoluble in theconcentrated 'liquor andconstitut'e a portion of the sludge, While.others comprise'a part of the soluble non-alkaline sodaretained in theliquor. It is not intended, however, to Vlimit the process to anyparticular mechanism or theory of action, and it suffices te state thatthe concentration of the contaminatednliquor vwith Ysubsequentclarification lto separate theprecipita'ted sludge` effectivelyV freesthe liquor substantiallyy completely'of the sodium.,o1'ganic.compounds`of the ,non- .alkalinesodaeffraction .which actn as settling andprecipi- .fungierte .targhgi. titanes.;

The concentration of the liquor to obtain the nonalkaline sodaprecipitate also results in a salting out or crystallization of asubstantial portion 'offthe sodium carbonate fraction of the non-causticsodain the cir-` culating liquor treated, since the solubility of thecarbonate decreases with increasing causticconcentration. Thus, thepurication of the liquor also provides a direct means of controllingprocess carbonation thereby reducing the carbonate soda concentration inthe'circulating liquor and maintaining a desirably high ratio of causticsoda to total soda (C/S=ratio of caustic soda, C, as free NaOH and ascombined in the form of sodium aluminate, and total soda, S, as causticsoda ,plus carbonate soda) in the process liquor. l

Accordingly, the present invention 4advantageously provides forimprovement in the quality or purity of the process liquor. Improvedquality or purity of the liquor, as used herein, is intended to meanthat the liquor after treatment contains less non-caustic soda,particularly the sodium carbonate fraction; less non-alkaline soda; andreduced concentration up to the point of substantial freedom of sodiumorganic compounds which are settling inhibitors and which adverselyaifect the effectiveness of starch in settling the red mud residue ofthe ore. The liquor purification process, as abovedescribed, isbenelcial to a variable degree in any case of alumina production by theWet alkali aluminate method depending upon the impurity level in theliquor; but is vital and necessary `to the operativeness of the Bayermethod applied to certain types of bauxites and laterites, such` as lWest Indian ores, if the red` mud residues are to be settled from theprocess liquor in a practical and successful marmer. Thus, the inventionprovides a means for establishing and maintaining a Bayer liquor of suchpurity that redmud residues` from these types of ores may be settled bythe use of a practical and necessarily limited amount of starch, whichoreresidues could not otherwise be processed at all.

In the application of the process in actual commercial practice the sizeor capacity of the purification operation is based on that required torectify thenon-caustic soda formed and/ or introduced in the circulatingprocess liquor percycle and the existing level of such impurities in theliquor, if any. The amount of non-caustic soda (s`o` dium carbonate andsodium organates) existing `and formed may be determined by appropriateliquor analysis and for any given liquor depends on many.` factorsincluding (1) the" natureof the bauxite.particularly the organic mattercontent, (2) the contribution of the starch in formation of sodiumorganates, (3) the sodium lcar- -bonate introduced with the causticizereiluent, and (4) other netV process carbonation includingcarbonate sodaformedtfrom the organic matter of the ore and starch. Accordingly thefraction of the" process liquor to be treated `per cycle is widelyvariable since it depends on the level of non-caustic impuritiesandtheamount of formation thereof per cycle, including both settlinginhibiting` organic compounds and sodiun carbonate.

Moreover, the fraction cut out to purication must alsobedeterminedwithfreference to the amount of noncaustic sodaprecipitated` as sludge, which in turn is dependent on` the level `orconcentration of the non-caustic impurities in the liquor being treated,the degree to which the "caustic liquor is `ctm'czentrated, and thedegree of separation of the sludge `or clarification of the vtreatedliquor. t

` Finally, the requisite degree of purification of the cir culatingliquor varies depending uponrelative difficulty ofsettling the `red mudresidues of` different alurninous ores, that is, fora givensftarch"consumption-certain residues will settle at practicaland?adequate` rates `at permissiblyhigher levels of liquorirnpurities.

`Therefore, the specidcandoptimlnn operating ctmditions mustnecessarilyfbe determined mpirically for' t without a significant holding each`particular case and such determination may readily be accomplished fromliquor analyses, and observation of the degree of improvement in oreresidue settling -rates at a desirably low starch feed rate (amount ofstarch based on the weight of mud treated).

It may be stated, however, that in general the concentration of theliquor should proceed to at least 350 grams per liter caustic soda (asequivalent Na2CO3) when confronted with non-caustic soda in Awhat may betermed normal amounts, although as indicated above, the particularcaustic soda concentration at which the gelatinous precipitate isobtained varies necessarily with the level or concentration of thenon-alkaline soda impurities in the liquor (and to some extent with thevarying specific composition of these impurities which is relativelyunknown and indeterminable), The amounts of both the slimy gelatinousprecipitate of the complex mixture of sodium organic compounds and thesodium carbonate precipitate may be increased by increasing the causticsoda concentration up to about 600` gramsper liter. However, the densityof the viscous caustic liquor is increased at such high concentrationsand tends to increase the difculty in separation of the sludgetherefrom. This is important in determining `optimum concentration`since maximum clariiication of the treated' liquor is an essentialobjective in practicing the purication process. In regard to specificconditions of the liquors investigated,it was found that caustic sodacon-- `centrations of from about 380 to about 500 grams per ALTERNATIVEPROCEDURES In the operation of the process of the invention, it has beenfound that in general an increase in liquor purity is obtained with thefollowing process Variations:

(l) Conducting the liquor concentration by a batch type operation whichis slower than the continuous type of salting evaporation generallycontemplated in the foregoing description.

(2) Holding the concentrated liquor, either at'concentration temperatureor allowing cooling, for a period sufcient to approach equilibriumconditions between the compounds in the precipitated sludgeand theirdissolved counterparts. This constitutes a means of obtaining theadvantageous result of the conditions under (1) above while operating onat least a semi-continuous basis.

(3) The liquor may be subjected to higher temperatures duringconcentration by operating the evaporator under pressure or Vwithreverse feed to obtain temper' atures above atmospheric boiling pointsof the liquor (for example inconcentrating to 450 grams/liter, backward'feed increased the temperature from about 250` F. to about 300 F.);.or

(4) Additions of very small but effective amounts of lime in anysuitable form to the concentrated liquor containing `the sludge prior toclarification either with or period before separation` of the sludge.

lThe advantages of the `inventionare fully indicated with reference tothe results described in` detail below in connection with the tabulateddata and the graphs and ow sheets of the drawings. Certain terms or``symbols referringrprimarily to` liquorco-mposition are employed belowand in the drawings and accordingly are hereby i defined as follows:

" The liquor composition in termslof alumina,

" uraoyl acetate method.

, 7 C=Caustic soda, that is, free NaOH plus NaOH corubned as sodiumaluminate as determined by titration to sodium hydroxide endpoint'.

S=Total soda, thatis, caustic soda plus soda as Na2CO3 (tot-al acidtitratable sod-a) as determined by titration yto total alkalinity endpoint. A=Alumina as determined by precipitation as l12O331-I20v byneutralization and subsequent calcination.

The (1) non-causticsoda, (2) non-alkaline soda, and (3) sodium carbonatecontents of the =liqulor `are then determined by difference. rlhus N.A.(non-alk. soda) =TNa-S=nonalkaline soda (so- `dium Organates) f In tbespecification Iand appended claims the concentrations are indicated ingrams per liter. Caustic soda (NaOH) is in all cases expressed asequivalent Na2CO3, and the ratios of these values are accordingly weightratios.

The `effect of the concentration of the liquor in removing non-causticsoda is clearly established from the data given in Table I below,wherein samples of contaminated liquor from a continuously operatedBayer process plant were subjected to concentration at atmosphericboiling temperatures by (l) batch evaporation and (2) continuousevaporation on a commercial scale, and thereafter the hotsludge-containing liquor was immediately pressure filtered as is:

Table I (1 BATCH EVAPORATION C l 169. 7 328. 5 407. 8 425. 5 472. l 542.6 619. 2 TNS. l 275. 9 185. 5 528. 0 544. 2 579. 7 652. 0 739 N.C./O..626 477 295 279 228 201 193 (2) CONTINUOUS EVAPORATION n 1A 2A. 3A 4A.

1 Grams per llter. 2 yN.C./G and N.A./O of untreated liquor was .514andati?, respectively. n Untreated liquor.

A comparison ofthe non-caustic soda to caustic soda ratios.(NC/Clindicates: that batch evaporation accomplishes a greaterreduction for a given caustic soda concentratiomor conversely,continuousevaporation requires a higher degree of concentration toobtain the same NC/C inthe liquor. ln either case, however, asubstantial portion of the non-caustic soda is removed from the liquorin the vform of a precipitated sludge.

In addition, runs 1A and 2A indicate a significant reduction innon-alkaline soda to caustic soda ratio, ie. from .190 to .170,`and-.157 to .145 or about 11% and 8%, respectively. The relativelysmall change in NA/C ratio cannot be taken as a criterion of theeiciency of the process in removing Vsodium organic compounds whichconstitute potent settling inhibitors. The heating on concentratingandthe strongcaustic liquor resulting apparently cause an increase inthe combinedznon-alkaline soda .present in thetreated liquor. This maybe due to decomposition of higher molecular weight sodium organates intolower molecular Weight organic compounds containing salt-forminggroupssuch as, -COOI-l, thus-increas ing the quantity of rtotal sodiumpresent as non-alkaline sodaby neutralizing more caustic soda. Inanyevent, theimprovement in settling rate on a lred niud residue, which yisparticularly Vcliliicult to'. Settle,

stirred for two minutes.

Sample 0 1A 2A 3A 4A Grams/liter s2. 5 133. s 15o. e 165. 1 173.5 249. 540o. 1 45o. 1 492. 1 515. 5 322. 1 475. 5 51e. 1 553. 5 575. 5 369. 6544. e 581. 2 629. 9 655. 2 72. 7 75. 2 G5. 7 61. 5 59. 0 120.1 141. 5130. 8 137. 9 135. 7 47. 4 es. s 55.1 76. 4 79. 7

Wt. ratios o. 331 o. 334 o. 334 o. 33s 0. 536 o. 774 o. 840 o. 873 o,889 o. 89s 0. 481 o. 362 9. 291 o. 280 o. 25s 0.190 Ao. 171 0.1.15 0.1550.154

SETTLING TESTS The untreated liquor 0 and the claried treated liquors1A, 2A, 3A and 4A were then employed in tests to determine settlingrates. The tests involved an actual single digest of bauxite in eachliquor inl order to reproduce as nearlyV as possible the red mudsettling conditions encountered in actual plant practice in Bayer liquorclarication, and subsequent settling tests on the-red mud residues. 1

Digestion.-An amount of untreated liquor (0) to give the equivalentof175 grams of caustic soda (as equivalent NaZCOa) was placed in astainless steel batch digester. 82 grams of Jamaican bauxite having aparticularly large red mud residue content of highly dispersible naturewas then added. From the liquor analysis and the known amount ofavailable alumina in the bauxite, an additional amount of aluminahydrate Was calculated and added to produce a charging ratio of aluminato caustic (A/ C) of 0.55 in the digester eliiuent. Water was then addedto bring the caustic soda concentration to 220 grams per liter. f

The digester was purged of air by sweeping with nitrogen and the orecharge was digested for l30 minutes at 200 C., the heat being suppliedVby a high pressure steam jacket. The digested slurry was cooled to C..by passing water throughthe jacket and the slurry was then ashed from165 C. to atmospheric pressure.` n

Settling rate.-The hot slurry was drained into a stainless steelbeakera'nd the volume adjusted to 975 Vml. to give a caustic soda (C)concentration of'180 g./l. The

" slurry was maintained at -its atmospheric boiling pointand-presolubilized starch in amount of 0.385% kbasedzon the weight ofred mud was added and the slurry was The starch solution was prepared asfollows: f n t 5 grams-of Maine potato starch was heated to 100 C. for25 minutes in 200 ml. of a 2.5% (by weight) NaOH solution. The solutionwas cooled and adjusted to a starch concentration of 20 g./l. 5 ml. ofthe starchV solution was added to the Ydigested slurry. Of the 82 gramsof bauxite charged, about 26` grams remains asV mud residue. The 5 ml.uof starch at 20 gV./l. is equivalent to 0.385% of the 26 gramsof redmud.` I"

The starch containing slurry Was placed in a 1000 ml. .Y graduateprovided with .a picket type "rake, the rake extending upward from thebottom to about one-half vthe depth of the graduate, and maintainedin'motion from a `centrally disposed rake shaft (to simulate the raksofTable Il SETTLING RATES-AS Is 1 sampm-. `o 1A 2A 3A 4A No/o .481 .352.291 28e 25s 1am/hrs p 1.3V 5.2 47 5.5 4.1

l Without adjustment of C/S to constant value.

2Settling rate calculated from observed rate. t i

The red mud settling rates obtained on the purified liquors in all caseswere between three and four times faster than that on the untreatedliquor.v

For purified liquor samples wherein thesludge was centrifuged offinstead of pressure ltered, the as is settling rates were:

Table 111 sample o 1B 2B 3B 4B n, mm2 1. a 4. 4 3.1 5.1 4. s

2 Settling rate calculated from observed rate.

, Table IV LIME TREA'IHED sAMPLlSS-IFSILTERED AND SETTLED samp1e 2n 3D4D n, mnr 7. 4 7. o 1. 2

v.These improved` settling rates were accompanied by a significantreduction in the non-alkaline soda to caustic soda ratio compared `tothe purified unlimed liquors, for example, 2A and 4A, in Table V below.`On the other hand, the carbonatesoda (Na2CO3) to caustic soda ratios didnot, shpw 4any appreciable change as follows:

through continuous concentration and immediate separation of sludge fromthe hot concentrated liquor is shown by the comparative data of Table VIbelow.

Thus, an important feature of the invention is the use of small buteffective amounts of `lime up toabout` 1% on the weight of the slurry(lter or centrifuge feed) to increase liquor purity. This`alternativeiis particularly advantageous where operating o`n` acontinuous plant scale and the advantageous holding periods attemperature (or with cooling and reheating) as shown in Table VI areless practical. 1

The fundamental contribution of the invention may be expressed in termsof increased eiciency of starch in red mud settling (as well as byincreased settling rates at lixed amounts of starch as shown in TableII, above).

The constant (free) settling rates of` untreated cohtaminated liquor, asynthetic liquor, and purified liquor were determined using the exacttest conditions set forth above under Settling Tests. `The results areshown in Table VII and in the graph of Figure 4 of the drawings.

. Table V11` p LIQUOR SAMPLE lMUD SETTLING RATE, FTJHR.

Starch2 A B C D Consumption Synthetic` Purified Purified Untreated No.1632 No. 1643 Too slow to measure. 5

l Liquor Descriptions: A-Synthetic A caustic aluminate liquor made upwith alumina hydrate, NaOH solution and N c1003 to give a syntheticspent liquor of approximately the same composition as untreatedcontaminated liquor D, except it contained no non-alkaline soda, Le.,all non-caustic soda was Na1CO3, and theY G/S ratio was 0.80 forsettling tests; DUntreated Bayer plant liquor composite sample of feedto the salting evaporator of an average C/S ratio of 0.752, and of whichone part had the composition of liquor 0 in Table I; B-No. 1632.Composite sample of centrifuge overliow Troma plant scale operation withthe addition of 0.75% slaked lime to the evaporator eliiuent. O =444grams per liter and C/S=.872; C-No.,1643. `.Composite sample ofcentrifuge overliow from a plant scale operation with the addition of0.75% slaked lime to the evaporator efduent. O =484 grams per liter, C/S.864.

2 Percent by Weight on red mud of presolubilized Maine potato starchadded after digestion.

to obtain aj, settling rate of 5 `feet perhour, the purified Table V l p1 Ummed and Limd and i Filtered Filtered sample. 2A 4A 2D l 4D Nil/o3.0.145 l 0.154 0.120 0.117 Nazooz/o n.145 `o. 114 0.142 0.111

This action of lime in increasing liquor purity with out decreasein theNaZCOg/C ratio is not `completely understood, bu t may be due to aocculating effect on the gelatinous sludge or a catalyzing effect ondegradation of the settling inhibiting organic compounds into insolublecompounds, while the caustic soda concentration of the liquor` is toohigh to permit any ,significant lime- Na2C03 reaction.` l. V i l y Theadditional` improvement in settling rates: obtained under conditionsallowing the liquor to more nearly appteashz .equilibrium sendtionses fOPI- 19Std t0 e. Straight.

liquor `16,43 requires less than 0.385% starch, the liquor 1632 onlyslightly over 0.4% while the `untreated liquor requires over 0.9%starch. .3 The foregoingresults `are innenced by the variations betweenC/S ratios in the respective liquors",y Howeven even thoughthe resultsreported combine the effect of the` removal ofl s odiunjl `carbonateA,with the effect` of removal andldegradation of `settling inhibitorsofthe nonalkaline soda, it is: correctly,representativeof conditionsestablished ina` plant liquor by the puriiicationlprocess, since it isone `of the accomplishments of @the invention to` control processcarbonation (reduce the `concentration of NazCOB inthe liquor).Moreover, litumust be noted that the `C/S ratios` attained Ainpurifyingthe liquorex cept liquor A,,where reduced, to `0.80 beforeconducting the. settling tests .in order to` more closelyapproximatesodium carbonate concentrations which would normally 1 l be maintainedin a blend of untreated and puriiied liquor in commercial plant scalepractice.

INCREASE IN PRECIPITATION RATE The increase in purity of circulatingliquor also leads to a significant increase in precipitation rate ofalumina from the green or pregnant liquors. It is recognized thataccumulation of organic matter, in particular, sodium organic compounds,in Bayer process liquor upon repeated recycling causes a rise infinishing ratio for a given length of time and a drop in aluminaproduction per unit of caustic liquor circulated. The amount of aluminaremaining in solution at the end of the precipitation cycle, as ameasure of yield, lis commonly expressed as `the so-called fnishingratio or A/C ratio of the spent liquor. A rise ininishing Vratiorepresents a drop in `alumina production,

Table IX belowrshows the significant increase in yield of aluminaobtained with a .purified liquor and a blend of purified and untreatedliquor, as compared with an untreated contaminated Bayer plant liquor.The'puriiied liquor was prepared by concentrating a sample of untreatedliquor to about 50.0 grams per liter caustic soda (expressed asequivalent Na2VCO3). The blend consists of a mixture of 50% purified and50% untreated liquor. The liquors were digested with calculated amountsof alumina hydrate to give the indicated A/ C ratios. Fine seed of traythickener quality was employed in a Weight ratio of seed to solublealumina of 1 to 2. During the first 24 hours of -the kprecipitationcycle the liquors were held at 150 F., the temperature being lowered to140 F. thereafter. The lbasic spent liquors analyzed as follows(concentrations in grams per liter):

Liquor A C S TN a C/S C/TNa Purified G4. 2 225 253 287 B89 785 Blended..c 63. 8 Y 224 290 320 772 700 Untl'euted. 63. 223 322 357 692 624 Theresults are shown as follows:

Table IX Y Purled Blend Untreated Precipitation Tlme l c Y v y A (hrs.)

A/C Percent A/C Percent AIC Percent Yield Yield Yield '.624 .620 .632409 34. 3 410 33. 7 421 33. 2 .375 39. 6 .376 39. 2 1 388 38. G .357 42.9 .362 41.4 .373 40. l) 328 47. 340 45. l 344 45. 7

117% hrs. Y These results areA graphically illustrated in Figure 3.

ysturen AND ,CAUsTrCIzrNG OPERATIONS rlfhe invention, as a furtherfeature, provides forfref covery and return Vof substantially allVof'thesoda and alumina removed lfronrthe cyclic Bayer system duringliquor purification. Y

- The sludge precipitated by concentration and separated by centrifuging(or filtering) into a high solids slurry is advantageously mixed with analumina-containing materialandthe mixture subjected to a sinteringoperation at zqjpr'opriate temperatures, for example, 1000 tol200 C.,

preferably 1050-1150 (orabout 1900.130 2l00 F.) to destroy -the organicmatter,v thus decomposing the sodium organatcs and also the sodiumcarbonate to form sodium aluminate with; ,the alumina inYthealumina-containing material and some excesssoda. Lime in properamount is added (usually in the formV` ofV CaCOa) to minimize reactionof soda and alumina with the silica in the aluinina-containingi materialand subsequent loss in silicate form. The sintered product is 'leached'with diluted caustic soda solution (eg. diluted causticzcr omtrent;spent liquor, or hydrate wash liquor) and the leach liquor obtainedcorresponds to a green caustic aluminate liquor ready for precipitation.Thus, the alumina of the ore, and the alumina in the mother liquor ofthe sludge, is substantially all recovered as sodium aluminate, theremaining fraction of the soda being substantially recovered as causticsoda.

The alumina-containing material fed to the sinter operation maybe anysuitable aluminous ore, the alumina' of which in a least substantialproportion forms sodium aluminate upon sintering by the well-knownlimesoda method. Preferably, the material is a fresh ore with. a highalumina to silica ratio for optimum eliiciency in recovery ofnon-caustic and/0r non-alkalinesoda Afrom the sludge throughcausticizing to sodium aluminate` and caustic soda. However, lowerlgrade bauxite ores of the high silica type, clay, or other siliciousaluminous ores; and ore residues, or mixtures of any o f kthese-materials with or without high grade bauxites may be employed withrecovery ofthe alumina and a major portion of the soda. Y K

Such material may in particular be a red mud residue obtained from thealkali aluminate Bayer process Ydigestion of a high silica aluminousore. The Bayer process as applied to high `silica ores results in alossY of about one pound of alumina and about vone pound of soda foreach pound of silica in the ore. The Yloss appears lin the, form of aninsoluble desilication product (a sodium aluminum silicate) which isprecipitated, andremoved with the insoluble red mud. The alumina in thered mud residues of such high silica bauxites `may be solubilized by thelime-soda sinter method, and a substantial part of the soda causticizedby formation of sodium alumnate. The sinter is then leached with dilutecaustic soda solution or spent liquor, and the caustic aluminate liquorreturned to the circulating Bayer process liquor for recovery of thealumina. Thus, red mud residues o f high silica ores may constitute allor a par-t of the alumina requirements and a part of the sodarequirementsof the sinter operation, while the soda-containing sludge,including both the gelatinous sodium organates and-the sodium carbonate,or a fraction enriched in the non-alkaline soda content and obtained asdescribed below, constitutes the balance of the soda requirements of.thesinter opere ation. c c The relative amounts of, theYsoala-containing sludge and alumina-containing material will depend, ofcourse, on the relative soda and alumina contents ofthese Vmaterials. Ingeneral, the proportions, including thel lime added, are adjusted toproduce a maximumv of solubilized alumina and soda, and a minimum ofsoluble silica. The -available'soda'jis usually maintained in Vslight'excess over that required to form sodium aluminate with the aluminacontent of the sinter feed, and' lime is added in slightl excess overthat requiredmt insolubilize thesilica,

With'rfresh aluminous ores, as opposed to soda-containing ore residues,the concentrated sludge usually constitutes all of the soda requirementsfor the sinter operation, although in some instancesv it may, besupple.- mented witht fresh soda ash. Also, as above-indicated, freshbauxite or other aluminous ore may behemployed in conjunction with or inplace of thesred mud residue; Accordingly the term aluminous ore,v as-used inthe specification and'claims embraces ore residues containingalumina, as wellas fresh` ores, and mixtures of such materials. p i v tAs an alternative, aj fractional centrifugingof` the precipitated sludgemay be accomplished'to give (1)'A high solids slurry of 50-60%k solidsby weightrichfin sodium carbonate and relatively lowin.V concentratedcaustic mother liquor containing alumina, and low in -the slimygelatinousV precipitate of sodium organates. i

(2)k Arlow solids slurry l5 to'30% yby weightf'rela? Y 13 tively lean insodium carbonate 'and high in" non-alkaline' soda sludge and motherliquor containing alumina.

The carbonate rich-low alumina and non-alkaline soda slurry is adaptableto direct causticizing to rectify the sodium carbonate to caustic soda.It contains aminimum of non-alkaline soda, which under ordinary limecausticizing conditions is not causticizable. Moreover, it is important,to reduce the alumina and caustic soda content in this causticizer feedsince most of the alumina would ibelost as insoluble calcium aluminatewhichgoes out with the lime sludge (CaCO3) formed and the caustic sodawould reduce eciency of the lime-soda reaction. As a further means oflowering the alumina and caustic soda concentrations of the causticizerfeed, it is recommended that the carbonate rich slurry be only afraction of the total feed, using fresh soda ash solution as thebalance.

The carbonate lean slurry, high in alumina containing motherrliquor andhigh in non-alkaline soda sludge advantageously constitutes a reducedload for thesinter operation and permits reduction in capacity ofequipment required. i

The overall` process is more fully described in conjunction with thefollowing example with reference to the accompanying drawings (Figures land 2).

EXAMPLE Referring to Figures 1 and 2, `there is shown schematic flowdiagrams of one preferred embodiment of the invention illustrating thepurification process wherein `spent liquor is concentrated and theprecipitated sludge is sep-` arated from the `concentratedliquor by`centrifuging with subsequent treatment of `sludge fractionsto `rectifythe soda (NaZO) and to recover the same as caustic soda (NaOH and sodiumaluminate), While also recovering the alumina in the liquor associatedwith the sludge. R

Referring now particularly to Figure 1, a selected fraction` ofcontaminated spent liquor `to be purified having the analysis indicatedon the ow sheet is introduced through line 1 into a salting typeevaporator wherein the liquor isconcentrated to a caustic sodaconcentration of 450 g./l. to obtain a slimy` gelatinous precipitate ofa portion of the non-alkaline soda or sodium organates and a precipitateof sodium carbonate. The precipitated sludge of non-caustic sodacompounds constitutes 3% by weight of the salting evaporator efuent andit is to be noted that the non-caustic to caustic soda ratio in theliquor dropped from 0.43 to 0.28 and the caustic to total soda ratioincreased from 0.78 to 0.87 in concentrat- Ving the liquor from acaustic soda concentration of unit to a low value which will permitapproximately maxi-v mum etliciency of the causticizing reactionconducted therein, that is, not less than about conversion ofl thesodium carbonate charged to the unit. The feed to the causticizing unitmay be fortified by the addition of fresh soda ash as indicated at 8 inthe iiow sheet; The lime for causticizing is charged at 9 into thecaustizing unit with 1.05 mols of lime being charged for each mol ofsodium carbonate in the liquor to be causticized. The causticizingoperation isconducted at artotal soda concentration of g./1. at theatmospheric boiling point of the liquor and produces a causticizereffluent as indicated at 11 having a caustic soda concentration of 135g./l. and a total soda concentration of 150 g./1. indicating that thecausticizing unit `operates `at a conversion factor of at least 90%yielding a caustic to total soda ratio in the liquorof at least 0.9. Thespecific caustic soda to total soda ratio in the causticizer eiuentliquor will vary somewhat depending upon the relative proportions ofsoda ash contributed by the centrifuge underflow slurry and by the freshsoda ash. For example, with 100% soda ash feed a C/S ratio of 0.953 hasbeen ob-` tained with a 50% soda ash-50% centrifuge underow feedto thecausticizer a C/S'ratio of 0.923 has been obtained.

The second fraction of separated precipitated sludge thickened to a 20%by weight solids content contains 81.5% of the solids` as sodiumcarbonate with a high concentration of 18.5% of its solids asnon-alkaline soda, that is, sodium organates `precipitated from theliquor by concentration. This fraction is passed through line 5 to asinteroperation 12 wherein it is mixed. with bauxite ore in `amount togive about 0.908 mol of alumina in the mixture per mol of soda in thesludge slurry from line 5. Also, lime is added in the amount of 2.1 molsper mol of silica in the ore charged to the sinter operation in order`to minimize loss of alumina from the bauxite and fromfthehsludge `as`insoluble sodium aluminum silicate. The sinter charge adjusted to theproper solids content is heated to a temperature approximating 19,50degrees F. after which the sintered product is charged through line 13to a leaching system. The sinter product is leached at 16 by theaddition of causticizer effluent liquor through line 14 diluted at 15with water. In the sintering operation` substantially all of thenonycaustic soda of the sludge is converted to sodium aluminate which isdissolved in the leaching system 16 by thefdilutedcausticizer eiiiuentliquor to produce a leaching eiuent' which is a sodium aluminateenriched caustic at 4 where the sludge is concentrated and separatedfrom `the concentrated liquor. to producefa highly clarifiedliquoncontaining only 0.5% solids by `weight `which is `recycled to themainline spentliquor as indicated. The

`till liquor having an alumina` to caustic soda ratio of '0.60. and acaustic concentration of g./l. The leaching system eliiuent isalsofortified in caustic soda from the soda producedin fthe sinteringoperation in excess of the amount combined with the alumina ofthe ore.Thisv liquor correspondingto ,Bayer process pregnant liquor may then becycled to the main plant precipitators for recovery `of the alumina,`while the causticizer emuent is cycled to the mainline `spent `liquorsystem for blending with the highcaustic soda concentration liquor,obtained from the centrifuge operation and the untreated spent liquor``for `recycling to. the main plant digesters of `the continuousBayerprocess. d

d Referring to FigureZ, there is` shown one embodiment byhwhichthesludge in the concentrated liquor is sepaalso in the liquorassociated with the sludge.` As a con` l r sequence, the non-causticsoda `content of the. slurry his substantially allin Athe fornrof thereadily causticiiable Ycausticizable or difricultly Acausticizablenon-alkaline soda ,bythe additionof water as `indicated at 7;,to` adjustthe h h asiunderow at `21 `and theyciariiied liquorcontaining` i`caustic sodaconcentrationof theliquor in the causticizing 71S` only"0.5 solids by `weight recycled tofthemainline sodium' carbonate .withaminimum content `of nonrated ,by` selective centrifuging` into the twoseparate fractions, oneconstituting causticizer feed and the otherconstituting the feed tofthe sinteroperatiou `as indicated infFigure`1.4.t A.

concentrated ,liquor having the `analysis as ing dicated in Figure `2and containing the precipitatedsludge in the `aintmnt of 3% soilidsbyweight is chargedthrough linetlS toa high speed disc-,type centrifuge19' where the sludgey is concentratedjto a\2`5%;solids` slurrydischarged spent `liquor through line 20. The partially concentratedsludge is introduced into a centrifuge of the solid bowl type wherein itis centrifuged at intermediate or moderately slow speeds to produce anunderliow 23 of 50% solids by Weight containing substantially all of thesolids as sodium carbonate as indicated in Figure' 1. This constitutesthe feed to the causticizer unit. 'This high solids slurryadvantageously contains a minimum amount of alumina having beenconcentrated to maximum solids content so that the loss of alumina ascalcium aluminate upon reaction with lime in the causticizing unit isreduced as far as possible'. The overflow from the bowl type centrifugecontaining 10% solids by weight and a major portion of the non-alkalinesoda or sodium organate compounds is introduced through line 24 toanother high speed centrifuge 25 whereiny the sludge is concentrated toa solids slurry (by weight). This underow 126 constitutes the feed tothe sinter operation set out in Figure l. The overflow from centrifugeis passed through line 27 to the mainline spent liquor system along withthe overflow from centrifuge 19, both of which contain only 0,5% solidsby weight.

It is to be understood that the invention is not limited to thefractionation of the precipitated sludge as indicated in Figures l and2. In certain instances, it may be much more desirable to charge all ofthe underflow from the centrifuging operation to the sintering operation172 of Figure l without cutting out any portion for direct causticizingin the causticizing unit 10 of Figure l.Y Accordingly, whether thecentrifuge operation involves f merely a single underliow or twoseparate underflows as indicated in Figures l and 2, it is to beunderstoodk that the invention embraces the concept of conducting thesintering and leaching operation on the total sludge obtained in theconcentrating evaporation of the puriiication process.

Regardless of the alternative procedure employed in this regard, itmaybe stated that the present invention as an additional feature thereofprovides for the recovery o f substantially all of the soda present asnon-caustic soda in the sludge separated from the concentrated liquorand in the liquor associated with the thickened sludge. In addition, byconducting the sinter operation on the sludge slurry, substantially allor a major portion of the alumina in the liquor of the slurry isrecovered as sodium` aluminate in the effluent from the leaching system.

Ihe present invention, as above-described, has its most advantageousapplication in the production of alumina from aluminous ores containingat least a portion of the available alumina in monohydrate form, andparticularly those ores characterized by a relatively large content ofred mud residue diiiicult to settle, that is, those ores lin theprocessing of which the liquor contamination becomes a vital factor.However, it is not intended to` limit the invention to any particulartype of aluminous ore, since the purification of any circulating causticaluminate liquor by the processl will produce benelici'al results interms of starch consumption, settling rate and alumina i precipitation.

Y Various modifications or equivalent stepsV may be adopted withoutdeparting'from the invention as defined by the scope of the appendedclaims. For example, any

suitable means effectivel to separate the precipitated sludge from theconcentrated liquor may be employed, the process not being, limited tomechanical features such as centrifuging or filtration, Vexcept as tothe specific embodiment involving fractional separation of theprecipitatedrsludge. 'Moreoveig the invention cannot be con'- strued aslimited to thertreatment `of the whole or any specific fraction of thecirculating process liquor since this merely involves such factors aseconomics vand capacity of equipment. In other" words, startingwithl Aapreviously contaminated liquor and without regard tokeconomicsrior".capacitylimitations, the entire liquor strcanifmaybepurified inone operation to the desired t. 'ns

minor fraction of the liquor per Bayer process cycle need be treated. lnactual'commercial operation the size of the fraction treated may bedetermined on the basis of t the amount of non-caustic soda to berectied to caustic soda iper cycle. In this regard, the amount ofnoncaustic soda separated and rectified will vary depending upon theparticular `treatment i.e., the concentration of caustic soda in theevaporator, and whether process alternatives are employed, such as (1) aholding periodV for the liquor prior to sludge separation, (2) limetreatment.

Regarding concentration of the caustic soda, it is not intended to limitthe invention in its generic aspectto any particular value, but itsuflices to state that the liquor must be concentrated sufciently toobtainthe slimy gelatinous precipitate characteristic of the insolubleportion of the non-alkaline soda, a substantial portion of the sodiumcarbonate of the non-caustic soda inherently salting out at thosecaustic concentrations effective to precipitate the insoluble sodiumorganates of the nonalkaline fraction.

Accordingly, theV invention is to be construed as to its tr-ue scope bythe claims appended hereto.

What is claimed is:

l. A process for the production of alumina from aluminous materials,which comprises digesting said materials in caustic soda-containingliquor, said aluminous materials containing organic matter which formssodium organic compounds in the liquor, removing the insoluble residuesof said aluminous materials from the digestion liquor by settling,recovering alumina by precipitation from the clarified liquor,concentrating the spent caustic liquor to a caustic soda concentrationsuiiicieut to precipitate a sludge containing sodium organic compounds,adding lime to the concentrated sludge containing liquor and separatingthe sludge from the liquor whereby to prevent, the sodium organiccompounds from exerting an inhibiting effect on the settling, insolubleresidues of said aluminous material from the digestion liquid, and

recycling the liquor of reduced settling-inhibiting sodium organiccompound content for ydigestion of additional aluminous material.

,2. Av ,continuous process for production Vof alumina from, aluminousymaterials containing organic `matter, whichjcomprises digestingsaidaluminous materials in recycled spent caustic aluminateliquor, removingthe insoluble residues of said aluminous material from the digestionliquor, by settling with addition of starch as a ilocculfating agent,`said starch and said organic matter of the aluminous material, formingsodium organic compounds andsodium `carbonate in the liquor, recoveringalumina byprecipitation fromythe clarified liquor, con` fractionV beingrectilied to caustic soda byV direct-lime 17 caustczng, and the otherfraction is mixed with 2,440,378 aluminous material sintered and leachedwith dilute 2,468,207 caustic soda liquor to recover the organiccompound 2,519,362 soda as sodium aluminate. 2,522,605 5 2,557,629

References Cited in the tile of this patent UNITED STATES BATENTS 1SNewsome et a1. Apr. 27, 1948 Kerr Apr. 26, 1949 Flint et al Aug. 22,1950 cumin sept. 19, 195o Boivent June 19, 1951 OTHER REFERENCESSherwin: Extractive Metallurgy of Aluminum in Journal of Metals, April1950, pages 661 to 667, in-

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nm 2,9e16o0April 25 1961 Johnl L., Porter It s hereby certified that error appearsin the above numbered patent requiring correction and that the saidLetters Patent should read as corrected below..

Signed and sealed this 24th day of VOctober 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of PatentsUSCOMM-DC

2. A CONTINUOUS PROCESS FOR PRODUCTION OF ALUMINA FROM ALUMINOUSMATERIALS ORGANIC MATTER, WHICH COMPRISES DIGESTING SAID ALUMINOUSMATERIALS IN RECYCLED SPENT CAUSTIC ALUMINATE LIQUOR, REMOVING THEINSOLUBLE RESIDUES OF SAID ALUMINOUS MATERIAL FROM THE DIGESTION LIQUORBY SETTING WITH ADDITION OF STARCH AS A FLOUCCULATING AGENT, SAID STARCHAND SAID ORGANIC MATTER OF THE ALUMINOUS MATERIAL FORMING SODIUM ORGANICCOMPOUNDS AND SODIUM CARBONATE IN THE LIQUOR, RECOVERING ALUMINA BYPRECIPITATION FROM THE CLARIFIED LIQUOR, CONCENTRATING THE SPENT LIQUORTO A CAUSTIC SODA CONCENTRATION SUFFICIENT TO PRECIPITATE A GELATINOUSSLUDGE OF SODIUM ORGANIC COMPOUNDS AND SODIUM CARBONATE WHEREBY TOPREVENT ACCUMULATION THEREOF IN THE LIQUOR IN AMOUNT